1. Technical Field
The present disclosure relates to a structure of connection between an optical unit and an optical path tube.
2. Related Art
In recent years, with the miniaturization of semiconductor process, the miniaturization of the transcription pattern in optical lithography of the semiconductor process has rapidly progressed. In the next generation, a fine processing of 20 nm or less will be demanded. Therefore, for meeting the demand of a fine processing of, for example, 20 nm or less, it is expected to develop an exposure apparatus in which an extreme ultraviolet light generating apparatus to generate an extreme ultraviolet (EUV) light with a wavelength of 13.5 nm and a reduced projection reflective optical system (reduced projection reflective optics) are combined.
As the EUV light generating apparatus, there have been proposed three types of apparatuses: an LPP (Laser Produced Plasma) type apparatus using plasma that is generated by irradiating a target material with a pulsed laser light, a DDP (Discharge Produced Plasma) type apparatus using plasma that is generated by discharge, and a free electron laser apparatus using electrons that are output from an electron accelerator.